The present relates to an electron beam device comprising an evacuated envelope formed by an optically transparent faceplate, a conical portion and a neck, an electron gun within the evacuated envelope and to a method of making the electron gun. In the present specification an electron beam device is to be understood to include cathode ray tubes, X-ray tubes, electron beam lithography apparatus, scanning and transmission microscopes, electron guns for scanning Auger mass spectrometers and also ion guns (not an electron beam device within the normal meaning of the term). For convenience of description, the electron beam device will be described with reference to a cathode ray tube.
Unpublished European Patent Application No. 86200481.9 discloses a cathode ray tube in which the electron gun comprises an elongate tubular substrate which has been vacuum formed on a bipartite mandril, a beam forming part comprising a number of deep drawn metal electrodes respectively bearing against a succession of stepped abutments formed interiorly of th tubular substrate and a lens part formed by helical prefocusing and focusing electrodes in a resistive film applied to the internal surface of the tubular substrate. Some of the electrical connections to the metal electrodes and to at least one point in the resistive film are made through the wall of the tubular substrate. Each of these electrical connections comprises a conical hole sand blasted through the substrate wall, an indium ball in the conical hole, which ball is contacted by a lead-out wire and conventional crystallizing glass for fusing together the component parts. Any part of the wires and/or indium balls protruding into the tube are cut-off flush. Although this type of electrical connection has been found to be generally satisfactory it has a number of disadvantages, especially from a manufacturing point of view. The electrical connection is complicated, and thereby, is expensive to make. It is not possible to ensure a good electrical contact with an electrode due to the use of the indium balls. Further the lead-out wires which are unsupported have to be held in position while the crystallizing glass is being baked.